Question

An object is placed at a distance of 10 cm from the concave mirror. Find the focal length of the mirror if

the image is formed at 30 cm in front of the mirror. Mention the sign convention of concave mirror.​

Answer 1

Given:

Focal length of concave mirror, f = -20 cm

Distance of object from the mirror, u = -10 cm

use formula, 1/v + 1/u = 1/f

or, 1/v = 1/f - 1/u

or, 1/v = 1/-20 - 1/-10

or, 1/v = -1/20 + 1/10 = 1/20

or, v = +20cm

hence, image position is the 20cm right side from the pole of the concave mirror as shown in the diagram. The image is straight and bigger than the object.

solution

Explanation:

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